1. Field of the Invention
This invention relates to circuit breakers and, more particularly, to circuit breakers having a force generating shunt for facilitating opening of contacts while maintaining contact pressure in opposition to contact repulsion forces for permitting a higher withstand.
2. Description of the Prior Art
Current limiting circuit breakers are used to limit fault currents. More particularly, they reduce to tolerable levels both the peak fault currents and thermal energy that reach downstream equipment. Mechanical and magnetic forces that can destroy equipment are proportional to the square of the peak currents (I.sub.p).sup.2, and thermal damage is proportional to the let through energy (I.sup.2 t). Moreover, current limiting circuit breakers not only perform the function of a circuit breaker and current limiting fuse, but are also resettable and reusable. These devices can also be effectively applied to motor control as well as to power distribution systems.
Two major factors control how well the current limiting phenomenon occurs; namely, how quickly the contacts separate after initiation of a fault current, and how quickly the impedance of the air arc develops, i.e., as the contacts separate an arc is drawn between them. The success of arc limiting requires a very high contact opening speed. The faster the contacts separate after initiation of the fault current, the shorter the dwell time of the arc acting on the contacts. Thus, the volume of melting and volatilization of the contact material is minimized.